Peter and Paul Snowden will chase a fourth Blue Diamond Stakes win with three acceptors in Melbourne's premier juvenile race.

However, one of their runners Bodyguard, must pass a fitness examination on Friday to run in the Group 1 race at Caulfield on Saturday after being deemed lame in a Racing Victoria veterinary inspection on Thursday.

The Snowdens took out the Blue Diamond together with Pride Of Dubai in 2015 while Peter was the head trainer for Sheihk Mohammed when Sepoy (2011) and Earthquake (2014) were successful.

One-time Blue Diamond favourite High Octane will be joined by Fearless who arrived from Sydney on Thursday morning to take his place as they work on Bodyguard to get him right to take his place.

The Snowdens had been tossing up whether to start Fearless who will be having his first start left-handed on Saturday.

They were concerned with gate 16 (he will jump from gate 14) in what can be a difficult assignment for two-year-olds having their first starts in Melbourne.

"He's a talented horse but it's a big ask to go there at your first start here," Peter Snowden said.

"A big field of 16 runners, it's not easy."

Snowden is loath to split High Octaine and a fit Bodyguard despite the latter scoring a comprehensive win in the Blue Diamond Prelude (1100m) on February 10 while the stablemate finished fifth after being held-up in the straight.

High Octane had been equally impressive in his debut victory in the Blue Diamond Preview (1000m) on January 26.

"I still don't know which one is better. I wish they both had the same amount of luck the other day," Snowden said.

"They work identical, they look identical as far as being great types, they're both very tractable, they do everything perfect, but they have to get it right on race day.

"High Octane did things wrong at his first start but raced a lot better last time, raced on the fence, and got around the corner well.

"He's had two runs there now and knows where he's going while Bodyguard is the ultimate professional."

Bodyguard was the only two-year-old of those inspected by RV vets on Thursday to have any issue and will be given the chance to show his fitness with another inspection on Friday.

RV vets will inspect Zestiman and Kuroyanagi also on Friday, once both two-year-olds are stabled in Melbourne.